Pregnancy Due Date Calculator
Calculate your estimated due date and track your pregnancy progress week by week with key milestones.
Calculation Method
First Day of Last Period
Average Cycle Length
Conception/Ovulation Date
IVF Transfer Date
Embryo Age at Transfer
Your Results
Estimated Due Date
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— days to go
Pregnancy Progress
Week 0
Week 1
Week 40
1st Trimester
Weeks 1-12
Early Pregnancy
2nd Trimester
Weeks 13-27
Mid Pregnancy
3rd Trimester
Weeks 28-40
Late Pregnancy
Key Milestones
First Ultrasound
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NT Scan / First Trimester Screen
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Anatomy Scan (20-week)
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Glucose Tolerance Test
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Full Term (37 weeks)
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How Due Date is Calculated
The due date is calculated using Naegele’s Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation on day 14.
For irregular cycles, the calculator adjusts by the difference from 28 days. Conception date method adds 266 days, as pregnancy actually lasts about 38 weeks from fertilization.
Understanding Trimesters
- 1st Trimester (Weeks 1-12): Organ development begins. Morning sickness common. Highest miscarriage risk period.
- 2nd Trimester (Weeks 13-27): “Honeymoon period” with less nausea. Baby movements felt. Anatomy scan performed.
- 3rd Trimester (Weeks 28-40): Rapid baby growth. More frequent checkups. Prepare for delivery.
Important Prenatal Tests
- First Ultrasound (6-8 weeks): Confirms pregnancy, checks heartbeat, and dates the pregnancy.
- NT Scan (11-14 weeks): Screens for chromosomal abnormalities like Down syndrome.
- Anatomy Scan (18-22 weeks): Detailed check of baby’s organs, spine, and development.
- Glucose Test (24-28 weeks): Screens for gestational diabetes.
Important Considerations
- Due date accuracy: Only about 5% of babies arrive on their exact due date. Most are born within 2 weeks before or after.
- Ultrasound dating: First trimester ultrasound is most accurate for dating, within 5-7 days.
- Full term range: Babies born between 39-40 weeks are considered full term. 37-38 weeks is early term.
- Consult your provider: Your healthcare provider may adjust your due date based on ultrasound measurements.